Anamorphic objective zoom lens

ABSTRACT

The anamorphic objective zoom lens includes, along an optical axis and in order from an object space to an image space: at least a negative (−) power spherical first lens group; an anamorphic second lens group, spherical third lens group preferably having positive (+) power, a variable power spherical fourth lens group and a positive (+) power spherical fifth lens group. The aperture stop is located before, after or preferably within the spherical fifth lens group. All spherical lens groups contain spherical and piano refractive optical surfaces. The anamorphic second lens group contains cylindrical and plano optical surfaces with at least one cylindrical surface oriented at substantially 90 degrees about at least one other cylindrical surface. The spherical first lens group may provide focusing. The variable power spherical fourth lens group provides zooming. The spherical third and fifth lens groups may provide compensation for thermal defocus.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of copending application Ser.No. 14/683,297 filed Apr. 10, 2015, which is a continuation is part ofcopending application Ser. No. 14/218,064, filed Mar. 18, 2014, whichapplication claims the benefit under 37 CFR §119(e) of U.S. ProvisionalApplication No. 61/808,343 filed Apr. 4, 2013, the contents of which areincorporated herein their entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO A “SEQUENCE LISTING”, A TABLE, OR A COMPUTER PROGRAMLISTING APPENDIX SUBMITTED ON COMPACT DISC

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to anamorphic objective zoom lenses, andmore particularly to a range of different focal length anamorphicobjective zoom lenses with zoom ratios that provide imaging over wide tonarrow fields of view and provide traditional anamorphic imagingcharacteristics, and potentially compact diameter by having anarrangement of five lens groups with spherical, anamorphic and sphericalpowers, in which one of the spherical lens groups following theanamorphic lens group has variable power and an optical stop locatedinside the last spherical lens group.

2. Description of Prior Art Including Information Disclosed Under 37 CFR1.97 and 1.98

Contemporary anamorphic objective zoom lenses normally have an opticalaxis and are commonly based on a rear anamorphic lens group or a frontanamorphic lens group. Anamorphic objective zoom lenses having a rearanamorphic lens group are typically more commonplace than anamorphicobjective zoom lenses having a front anamorphic lens group.

Anamorphic objective zoom lenses having a rear anamorphic lens grouphave a rear lens group with Y cylinder refractive optical surfaces and afront spherical lens group with an optical stop in the front sphericallens group in the form of a variable aperture diameter iris ordiaphragm.

This anamorphic objective zoom lens arrangement produces images havingspherical out of focus objects commonly referred to as the bokeh ascompared to the oval or elliptically shaped out of focus objectsproduced by fixed focal length (commonly referred to as prime)anamorphic objective lenses. The oval or elliptically shaped bokeh ofout of focus objects are desired by cinematographers because theyproduce a distinctive artistic look that is different from sphericalobjective lenses. Another common drawback with this anamorphic objectivezoom lens arrangement is that the full aperture may be relatively slowas compared to that of anamorphic prime lenses.

Anamorphic objective zoom lenses having a front anamorphic lens grouphave a front lens group with X cylinder refractive optical surfaces anda rear spherical lens group with an optical stop in the rear sphericallens group in the form of a variable aperture diameter iris ordiaphragm.

This anamorphic objective zoom lens arrangement produces images havingoval or elliptically shaped out of focus objects commonly referred to asthe bokeh which is desired by cinematographers for the reasonspreviously given however these lenses normally provide only small zoomratios of 2× or 3×, where the smaller zoom ratio provides the widestfield of view, and they tend be large in diameter with correspondingpotentially higher weight and cost. They may also exhibit some breathingwhen focusing where the breathing is characterized by the field of viewor focal length of the lens changing size as the lens is focused fromdistant to close objects or vice versa. In addition they may alsoproduce a thermally induced focus shift with change of temperature wherethe focus shift is not constant over wide to narrow fields of view andthe image is characterized by having residual astigmatism. Neverthelessthe front anamorphic objective zoom lens arrangements produce imageshaving numerous residual optical aberrations and characteristics most ofwhich are desired by cinematographers because they produce an artisticlook that is different from spherical objective lenses.

Many of the less desired residual optical aberrations andcharacteristics of these front and rear anamorphic objective zoom lensarrangements were accepted by cinematographers with film based camerasbut with the advent and adoption of electronic sensor based digitalcameras some of them have become less acceptable. In particular theamount of residual chromatic aberration has become less tolerablewhereas some field curvature combined with some residual astigmatism isstill acceptable.

As well as the oval or elliptically shaped bokeh another characteristicthat is desired because of the distinctive artistic look produced is thedepth of field being different in the vertical azimuth direction of thefield versus the horizontal azimuth direction of the field. In the caseof an anamorphic objective zoom lens that squeezes the horizontal fieldof view by substantially two times as compared to the vertical field ofview, the depth of field in the horizontal azimuth direction of thefield is substantially two times greater than the depth of field in thevertical azimuth direction of the field.

Improving the optical aberrations and characteristics of anamorphicobjective zoom lenses of this arrangement may involve increasing opticalsurface shape complexity and hence manufacturing cost including addingaspherical and free-form shaped optical surfaces.

Thus, to address the artistic need of cinematographers and maximize theimaging potential of both film and digital cameras a compact diameteranamorphic objective zoom lens arrangement that provides a useful zoomrange going from wide to narrow fields of view during zooming with asuitable blend of residual optical aberration correction andcharacteristics needs to be achieved.

Lenses of this type tend to be sensitive to changes in temperature andwill go out of focus without some means of compensating for temperatureshifts. Accordingly, there is a need for including some means ofproviding thermal compensation to maintain the focus over thetemperature range in which the lens will operate.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to an anamorphic objective zoom lensincluding, along an optical axis and in order from an object space to animage space, at least a negative (−) power spherical first lens group:an anamorphic second lens group, a spherical third lens group preferablyhaving a positive (+) power, a variable power spherical zoom fourth lensgroup and a positive (+) power spherical fifth lens group wherein anaperture stop is located before, after or preferably within thespherical fifth power lens group. The anamorphic second lens group hasat least one cylindrical surface in a first direction and at least oneother cylindrical surface in a substantially perpendicular direction tothe first direction to enable a high degree of aberration correctionover the whole image, whereby the residual longitudinal chromaticaberration and the residual lateral chromatic aberration aresubstantially reduced. The variable power spherical fourth lens grouphas at least two lens sub groups that are axially movable to providezooming. The negative power spherical first lens group may providefocusing by movement of at least one of the lens elements containedtherein and may exhibit low breathing in the focus range. Lens elementsof the spherical third and fifth lens groups are independently axiallymovable by active or passive or active and passive means whilepreferably maintaining the overall length of the anamorphic objectivezoom lens to provide thermal compensation of defocus which isconsistently small and has little astigmatism through focusing andzooming. The lens is a complete assembly that forms a real image.

The anamorphic second lens group provides a squeeze of the field of viewso that the focal lengths in the X and Y directions are different by aratio of about two times which is typical for traditional anamorphicoptical systems. The positive power spherical fifth lens group adjacentthe image space delivers the radiation passing through the opticalsystem on to the image sensor with nearly telecentric light paths andsuitably high relative illumination, thereby increasing the efficiencyof many electronic sensors.

The variable power spherical zoom fourth lens group which provideszooming uses at least two axially movable lens sub groups. The variablepower spherical zoom fourth lens group is located between object spaceand the optical stop thus providing a substantially near constantaperture through zoom.

The lens elements of the spherical third and fifth lens groups whichprovide thermal compensation of defocus through focusing and zooming canbe independently axially moved by active means employing motors orpassive means utilizing materials exhibiting suitable thermal expansioncoefficients in the mechanical support of the lens elements or acombination of both means. The thermal compensation of defocus byactive, passive or combined means has the additional advantage of notrequiring the operator of the lens to refocus the lens and theassociated loss of focus scale calibration. The thermal compensation ofdefocus by passive means has the additional advantage of not requiringthe complexity of a power source for motors.

In accordance with one aspect of the present invention, an anamorphicobjective zoom lens is provided including, along an optical axis and inorder from an object space to an image space, a negative (−) powerspherical first lens group; an anamorphic second lens group, a sphericalthird lens group preferably having a positive (+) power, a variablepower spherical zoom fourth lens group and a positive (+) powerspherical fifth lens group and an aperture stop. The aperture stop islocated in a position either before, after and within the sphericalfifth lens group. At least one lens element of said spherical third lensgroup and at least one lens element of said spherical fifth lens groupare independently axially adjustable to compensate for thermal defocusin image space for at least two focal lengths within the focal lengthrange.

Preferably, the lens elements of the spherical third lens group aremoveable together, the lens elements of the spherical fifth lens groupare moveable together, and the spherical third lens group and thespherical fifth lens group are independently axially adjustable tocompensate for thermal defocus in image space for at least two focallengths within the focal length range.

Preferably, the aperture stop is located within the positive (+) powerspherical fifth lens group.

The negative (−) power spherical first lens group is configured toprovide focusing.

The anamorphic objective zoom lens has an optical axis. The first,second, third, fourth and fifth lens groups are situated along theoptical axis. The anamorphic objective zoom lens is adapted for usebetween an object space and an image space. The optical axis extendsbetween the object space and the image space.

The fifth lens group has at least one cylindrical surface in a firstdirection and at least one cylindrical surface in a directionsubstantially perpendicular to the first direction.

The fifth lens group has focal lengths in the X and Y directions whichdiffer and together with the other lens group focal lengths producefocal lengths in X and Y directions which differ by a ratio of about twotimes.

The anamorphic objective zoom lens preferably has a focal length withinthe range of from at least 35 mm to 140 mm and preferably 40 mm to 125mm in the Y direction.

The anamorphic objective zoom lens provides low residual chromaticaberration, a traditional oval bokeh shape, and different depths offield in the vertical and horizontal azimuth directions of the field.

The anamorphic objective zoom lens has a medium fast full aperture,moderately wide angle field of view to a moderately narrow angle fieldof view throughout its zoom lens range.

The lens groups of the anamorphic objective zoom lens are fabricated oflens elements made of glass.

The spherical lens groups include a lens element with a rotationallysymmetrical surface shape about the optical axis.

The lens group with anamorphic powers includes a lens element with anon-rotationally symmetrical surface about the optical axis.

The anamorphic objective zoom lens preferably operates at an aperture off/3.1 and over a waveband of 455-656 nm.

The anamorphic second lens group has seven cylindrically surfaced lenselements with eight Y cylinders, five X cylinders and one plano surfaceshapes.

The spherical first lens group includes five lens elements, three ofwhich are axially moveable relative to the other.

The spherical third lens group includes four lens elements.

The spherical zoom fourth lens group includes five lens elements, threeof which form a first zoom sub group and two of which form a second zoomsub group, both of which are axially movable.

The spherical fifth lens group includes nine lens elements.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF DRAWINGS

To these and to such other objects that may hereinafter appear, thepresent invention relates to an anamorphic objective zoom lens asdescribed in detail in the following specification and recited in theannexed claims, taken together with the accompanying drawings, in whichlike numerals refer to like parts and in which:

FIG. 1 is a lens plot in the YZ elevation (side view) and XZ elevation(plan view) on an optical axis Ø where the Y direction focal length is51.00 mm and the X direction focal length is 26.21 mm. In the YZelevation, three fields are shown at zero, top and bottom of the fieldof view. In the XZ elevation, three fields are shown at zero and bothsides of the field of view. In the YZ elevation and in the XZ elevationdiagrams an intermediate focus distance arrangement is shown;

FIG. 2 is a lens plot in the YZ elevation (side view) on an optical axisØ where the Y direction focal lengths are 40.01 mm, 67.98 mm and 125.01mm with three fields shown at zero, top and bottom of the field of viewand the top to bottom diagrams showing far, intermediate and close focusdistance arrangements; and

FIG. 3 is a lens plot in the XZ elevation (plan view) on an optical axisØ where the X direction focal length are 20.57 mm, 34.94 mm and 64.27 mmwith three fields shown at zero and both sides of the field of view andthe top to bottom diagrams showing far, intermediate and close focusdistance arrangements.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to anamorphic objective zoom lenses, and inparticular to a range of different focal length anamorphic objectivezoom lenses covering at least a focal length range from 35 mm to 140 mmand preferably 40 mm to 125 mm in the Y direction and providing lowresidual chromatic aberration, a traditional oval bokeh shape anddifferent depths of field in the vertical and horizontal azimuthdirections of the field.

The term “lens group” as used in connection with the anamorphicobjective zoom lens disclosed herein means one or more individual lenselements. Also, the terms “optical stop” and “stop” are equivalent termsthat can be used interchangeably.

The example provided herein is a preferred embodiment of the inventionin which the first (front) lens group is negatively powered, the thirdlens group is positively powered, the fourth lens group is variablepowered and the last (rear) lens group is positively powered. Those lensgroups are paired with an anamorphic second lens group to work in unisonand match the preferred optical interface characteristics of sensors,where near telecentric radiation beams approach the sensor.

The preferred embodiment discussed below is a medium fast full aperturemoderately wide angle field of view to moderately narrow angle field ofview anamorphic objective lens of the zoom.

In the preferred embodiment, all of the lens elements are made fromglasses. The lens element optical surface shapes in the first, third,fourth and fifth spherical lens groups are all rotationally symmetricalabout the optical axis such as spherical and in the anamorphic secondlens group at least one lens element surface shape is non-rotationallysymmetrical about the optical axis such as cylindrical.

In addition to providing these kinds of features and others like lowbreathing and (near) telecentric radiation output at the sensor, thepreferred embodiment is capable of achieving suitable levels of variousperformance including image quality resolution and contrast (usuallymeasured as MTF), high relative illumination for low shading andefficient optical throughput at the sensor via near telecentricradiation output at the sensor, which telecentric radiation output isless than 10 degrees.

The preferred embodiment of the present invention will now be describedby way of a design example with accompanying figures and tables.Referring first to FIG. 1, each lens element is identified by a numeralfrom 1 through 30 and the general configuration of each lens element isdepicted, but the actual radius of each lens surface is set forth belowin a table. The lens surfaces are identified by the letter “S” followedby a numeral from S1 through S58.

Each lens element has its opposite surfaces identified by a separate butconsecutive surface number as, for example, lens element 1 has lenssurfaces S2 and S3, lens element 11 has lens surfaces S21 and S22 and soforth, as shown in FIG. 1, except that for doublet lens element pairs 3,4 and 14, 15 and 18, 19 and 23, 24 the coincident facing lens surfacesare given a single surface number. For example, doublet lens elementpair 3, 4 is comprised of lens element 3 having a front lens surface S6and a rear lens surface S7 and lens element 4 having a front lenssurface S7 (coincidental) and a rear lens surface S8. The location ofthe object to be photographed, particularly as it relates to focusdistance, is identified by a vertical line and numeral “S1” on theoptical axis, and the real image surface is identified by the numeralS59. All of the spherical lens surfaces have a finite radius ofcurvature except S10 which is piano and all the cylindrically surfacedlens elements have a finite radius of curvature in X or Y directionsexcept for S14 which is piano.

Before describing the detailed characteristics of the lens elements, abroad description of the lens groups and their axial positions andmovement will be given for the anamorphic objective zoom lens system ofthe present invention, generally designated 50. Beginning from the endfacing the object S1 to be photographed. i.e. the left end in FIG. 1,the spherical first lens group G1 comprises lens elements 1 and 2 and alens sub group SG11 comprised of lens elements 3, 4 and 5. Theanamorphic second lens group G2 comprises lens elements 6, 7, 8, 9, 10,11 and 12. The spherical third lens group G3 includes lens elements 13,14, 15 and 16. The variable power spherical zoom fourth lens group G4includes, from left to right in FIG. 1, lens sub group SG41 includinglens elements 17, 18, and 19, and lens sub group SG42 including lenselements 20 and 21. The spherical fifth lens group G5 closest to theimage space includes lens elements 22, 23, 24, 25, 26, 27, 28, 29 and30.

The images of FIG. 2 illustrate in the Y direction the movement of lenssub group G11 in both directions along the optical axis for focusing atthree focus positions and the movement of lens sub groups SG41 and SG42in both directions along the optical axis for zooming at threepositions.

The images of FIG. 3 illustrate in the X direction the movement of lenssub group G11 in both directions along the optical axis for focusing atthree focus positions and the movement of lens sub groups SG41 and SG42in both directions along the optical axis for zooming at threepositions.

In FIGS. 2 and 3 the auxiliary lens fifth group G5 remains stationaryand at a fixed distance from the real image surface S59.

While only the lens elements are physically shown in FIG. 1, it is to beunderstood that conventional mechanical devices and mechanisms areprovided for supporting the lens elements and for causing axial movementof the movable lens groups in a conventional lens housing or barrel.

The Optical Prescription data for the above described anamorphic zoomlens system 50 is set forth below in TABLE 1, which is extracted fromdata produced by CODE V® optical design software that is commerciallyavailable from Synopsis Optical Research Associates, Inc. Pasadena,Calif., U.S.A., which was also used for producing the optical diagrams.All of the data in TABLE 1 is given at a temperature of 25° C. (77° F.)and standard atmospheric pressure (760 mm Hg).

Throughout this specification, including the Tables, all measurementsare in millimeters (mm) or as otherwise shown. In TABLE 1, the firstcolumn “ITEM” identifies each optical element and each location, i.e.object plane, etc., with the same numeral or label as used in FIG. 1.The second and third columns identify the “Group” and “Subgroup”,respectively, to which that optical element (lens) belongs with the samenumerals used in FIG. 1. The fourth column “Surface” is a list of thesurface numbers and the fifth column “Shape” is the surface shape.

The sixth and seventh columns “Focus Position” and “Zoom Position”,respectively, identify the typical focus positions of the spherical lensgroup and the typical positions of the lens elements in the variablepower spherical zoom fourth lens group wherein there are changes in thedistance (separation) between some of the surfaces listed in the“Separation” column which is the axial distance between that surface(fourth column) and the next surface, for example, the distance betweensurface S2 to surface S3 is 5.579 mm.

The columns headed by the legends “Y Radius of Curvature” and “X Radiusof Curvature” list the optical surface radius of curvature for eachsurface in the Y and X plane, respectively, with a minus sign (−)meaning the center of the radius of curvature is to the left of thesurface, as viewed in FIG. 1, and “Flat” meaning an optically flatsurface described as “Plano” in column 5.

The next four columns, 11 to 14, of TABLE 1 relate to the “Material”between that surface and the next surface to the right in FIG. 1, withthe eleventh column “Type” indicating whether there is a lens (Glass) orempty space (Air) between those two surfaces. All of the lenses areglass and the column titled “Code” identifies the optical glass. Thecolumn marked “Supplier” identifies the source of the lens and thecolumn marked “Name” lists the Supplier's identification for each glasstype, but it is to be understood that any equivalent or adequate glassmay be used.

The last column of TABLE 1 headed “Aperture Half Diameter” provides themaximum aperture half diameter for each surface through which the lightrays pass.

The novel configuration of having a negatively powered spherical firstlens group, an anamorphic second lens group followed by a sphericalthird lens group preferably with a positive power, a variable powerspherical fourth lens group and a positively powered spherical fifthlens group containing an optical stop may produce some residualdistortion, astigmatism and field curvature aberrations but thoseaberrations to a tolerable extent contribute to the anamorphic look asdesired by many cinematographers. In addition, a balanced blend of theafore-described lens characteristics may aid in cost reduction ofmanufacture. With the advent and adoption of digital cameras employingelectronic sensors a large back focal length which was once required forfilm cameras having a reflex mirror may be less necessary but is stillprovided for in the novel anamorphic objective zoom lens.

The preferred embodiment operates at an aperture of f/3.1 and over awaveband of 455-656 nm and this waveband is what was used in the MTFTable 3. A faster or slower aperture may be required and an extendedwaveband may be required. The aperture may be increased or reduced andthe waveband expanded and the optical designs re-optimized to maximizeimage quality over such apertures and wavebands without departing fromthe invention. Also, during such re-optimization alternate glass typesmay be used without departing from the spirit and scope of thedisclosure. Furthermore, more complex optical surface shapes such asaspherical and free-form surfaces may be introduced for expandedperformance but at the likely effect of increased manufacturing cost.

Referring to FIGS. 1-3, those figures relate to the preferred embodimentin which the focal length in the Y directions are 40.01 mm, 67.98 mm and125.01 mm and in the X directions are 20.57 mm, 34.94 mm and 64.27 mm.The overall length is 477 mm from the first refractive surface vertex ofthe lens to the image surface vertex, the front diameter clear apertureis 114.00 mm, the back focal length from the rear refractive surfacevertex to the image vertex is 37.17 mm and the close focus distance fromthe object to the image is 1165 mm. The focal lengths of the sphericalfirst lens group are −116.86 mm, −118.72 mm and −120.67 mm for the far,intermediate and close focus distances. The focal lengths of theanamorphic second lens group are +306.23 mm in the Y direction and−284.96 mm in the X direction. The focal length of the spherical thirdlens group is 107.33 mm. The focal lengths of the spherical fourth lensgroup with zooming are −90.88 mm, −100.10 mm and −70.74 mm for theshort, medium and long focal length positions. The focal length of thespherical fifth lens group is 86.52 mm. The focal lengths of thefocusing sub group and the zooming sub groups respectively are −265.40mm, −46.15 mm and 190.83 mm.

FIGS. 2 and 3 show the locus of axial movement of the focusing sub groupwith a long dashed curve and the locus of axial movements of the zoomingsub groups with short dashed curves where the closest approach of thezooming sub group nearest image space to the adjacent stationary lenselement lies between zoom positions three (Z3) and five (Z5), of whichthe axial airspace distance of closest approach is given approximatelyby the data for zoom position Z4 in Table 1 which accompanies thisspecification.

The focal lengths of the seven anamorphic lens elements containing atleast one cylindrical surface are in order from an object space to animage space −75.75 mm (in X direction), −150.63 mm (in X direction),−561.89 mm (in Y direction), 87.29 mm (in X direction), 141.59 mm (in Ydirection), −3906.70 mm (in Y direction) and −230.05 mm (in Ydirection). It is to be understood that the focal lengths of the sevenanamorphic lens elements in the other X and Y directions aresubstantially large and hence have little optical power.

In the preferred embodiment the lens system includes a total of thirtylens elements with twenty two singlets and four doublets. The sphericalfirst lens group contains five lens elements with three elements axiallymovable for focusing at different distances, the anamorphic second lensgroup contains seven cylindrically surfaced lens elements with eight Ycylinders, five X cylinders and one plano surface shape, the sphericalsecond group contains four lens elements, the zoom fourth lens groupcontains five lens elements which form two axially movable sub groupsfor zooming with three lens elements and two lens elements. The opticalstop lies within the spherical fifth lens group. The nominal image sizeis 8.91 mm vertical half height and 10.65 mm horizontal half width inimage space. In this example embodiment the telecentric radiation outputis about 9.1 degrees at all three focus positions and over the zoomrange.

The accompanying Optical Prescription Table 1 describes a select exampleof the preferred embodiment of the anamorphic objective zoom lensdisclosed herein.

Table 2 which accompanies this specification contains focal length,anamorphic squeeze, illumination and breathing data of the preferredembodiment. In Table 2 it is shown that the anamorphic squeeze ratio iswithin a small range of about 1.95% to 2.03%. In Table 2 it is alsoshown that the relative illumination is above 30%, which is sufficientlyhigh for low shading at the corner of the field of view when ananamorphic objective zoom lens is used in combination with an electronicsensor at the image plane, such as when the anamorphic objective zoomlens constitutes part of a digital camera. In Table 2 it is furthershown that the focus breathing is consistently very small throughfocusing and zooming.

In Table 3 which accompanies the specification, the polychromatic MTFperformance at a spatial frequency of 20 cycles/mm is shown for theexample embodiment to be greater than 50% at all field positions at thegiven combination of far, intermediate and close focus distances andshort, medium and long focal lengths at a temperature of 25° C. (77° F.)and standard atmospheric pressure (760 mm Hg).

In Table 4 which accompanies the specification, the polychromatic MTFperformance at a spatial frequency of 20 cycles/mm is shown for theexample embodiment to be greater than 50% at all field positions at thegiven combination of far, intermediate and close focus distances andshort, medium and long focal lengths at a temperature of 40° C. (104°F.) and standard atmospheric pressure (760 mm Hg). The third and fifthlens groups are axially moved to compensate for thermal defocus. Themovements are given by respectively changing the separations of surfacesS24, S31, S50 and S58 by −0.126 mm, +0.126 mm, +0.054 mm and −0.054 mm.

In Table 5 which accompanies the specification, the polychromatic MTFperformance at a spatial frequency of 20 cycles/mm is shown for theexample embodiment to be greater than 50% at all field positions at thegiven combination of far, intermediate and close focus distances andshort, medium and long focal lengths at a temperature of 10° C. (50° F.)and standard atmospheric pressure (760 mm Hg). The third and fifth lensgroups are axially moved to compensate for thermal defocus. Themovements are given by respectively changing the separations of surfacesS24, S31, S50 and S58 by mm, +0.126 mm, −0.126 mm, −0.054 mm and +0.054mm.

In Tables 4 and 5 the polychromatic MTF of the anamorphic objective zoomlens system 50 has been computed theoretically in accordance withaccepted optical principles and programs such as CODE V® optical designsoftware. The glass coefficients of refractive index and expansion withtemperature were obtained from commonly available data publicationsproduced by the vendor corporations Ohara and Schott. All opticalsurface separations between lens elements are thermally controlled bythe expansion and contraction of metal spacers made of aluminumcontacting the optical surfaces at their clear apertures which are twotimes the aperture half diameter values given in Table 1. Thetemperature range of the anamorphic objective zoom lens system 50, asdesigned and as described herein, is 10° C. (50° F.) to 40° C. (104° F.)with a nominal design temperature of 25° C. (77° F.). However, thisanamorphic objective zoom lens system will maintain a high level ofperformance over at least an extended range of −10° C. to 50° C.,although some degradation of image quality may be observed at lowtemperatures.

The seven anamorphic lens elements with the cylindrical surfaces of theexample embodiment additionally may each have two refractive surfaceswhich may be formed by X and Y cylindrical surfaces or Y and Xcylindrical surfaces with the X and Y surfaces substantiallyperpendicular to one another. This arrangement may improve the imagingcharacteristics but likely at the effect of additional manufacturingcost.

Although the present invention has been fully described in connectionwith a preferred embodiment thereof with reference to the accompanyingdrawings and data tables, various changes and modifications could bemade thereto, including smaller and larger zoom ranges, smaller andlarger focal lengths, smaller and larger anamorphic squeeze ratios,smaller and larger full aperture f/numbers, smaller and larger imagesizes, smaller and larger wavebands, etc. (e.g., 435 nm to 656 nm), aswill be apparent to those skilled in the art. Such changes andmodifications are to be understood as being included within the scope ofthe present invention as defined by the appended claims.

TABLE 1 Optical Prescription Y Radius of X Radius of Sub- Surface FocusZoom Separation Curvature Curvature Item Group Group No. Shape¹ PositionPosition^(2,3) (mm) (mm) (mm) Object S1 Plano F1 All 999999.000 FlatFlat Plane F2 All 1965.000 F3 All 943.000 1 G1 S2 Sph. All All 5.579364.892 364.892 S3 Sph. All All 0.450 84.772 84.772 2 G1 S4 Sph. All All11.657 79.239 79.239 S5 Sph. F1 All 39.560 105.024 105.024 F2 All 30.907F3 All 22.175 3 G1 SG11 S6 Sph. All All 6.899 −585.944 −585.944 4 G1SG11 S7 Sph. All All 4.873 −303.627 −303.627 S8 Sph. All All 5.832495.133 495.133 5 G1 SG11 S9 Sph. All All 4.517 −261.296 −261.296 S10Plano F1 All 11.045 Flat Flat F2 All 19.697 F3 All 28.430 6 G2 S11 XCyl. All All 4.337 Flat −82.662 S12 X Cyl. All All 9.184 Flat 70.673 7G2 S13 X Cyl. All All 4.249 Flat −75.084 S14 Plano All All 1.385 FlatFlat 8 G2 S15 Y Cyl. All All 4.959 −908.544 Flat S16 Y Cyl. All All4.334 920.220 Flat 9 G2 S17 X Cyl. All All 14.948 Flat 263.078 S18 XCyl. All All 4.367 Flat −88.994 10 G2 S19 Y Cyl. All All 11.981 246.798Flat S20 Y Cyl. All All 7.962 −161.076 Flat 11 G2 S21 Y Cyl. All All27.028 69.953 Flat S22 Y Cyl. All All 15.808 58.918 Flat 12 G2 S23 YCyl. All All 3.800 −76.352 Flat S24 Y Cyl. All All 3.889 −232.274 Flat13 G3 S25 Sph. All All 10.900 137.891 137.891 S26 Sph. All All 0.519−214.419 −214.419 14 G3 S27 Sph. All All 3.550 259.088 259.088 15 G3 S28Sph. All All 14.662 64.133 64.133 S29 Sph. All All 0.500 −353.262−353.262 16 G3 S30 Sph. All All 8.144 97.834 97.834 S31 Sph. All Z17.030 635.356 635.356 All Z2 26.780 All Z3 46.204 All Z4 64.237 All Z575.329 17 G4 SG41 S32 Sph. All All 2.200 −159.777 −159.777 S33 Sph. AllAll 5.133 58.576 58.576 18 G4 SG41 S34 Sph. All All 2.200 −77.157−77.157 19 G4 SG41 S35 Sph. All All 5.066 53.293 53.293 S36 Sph. All Z143.249 880.564 880.564 All Z2 40.464 All Z3 34.324 All Z4 21.994 All Z56.735 20 G4 SG42 S37 Sph. All All 2.800 180.566 180.566 S38 Sph. All All1.047 109.323 109.323 21 G4 SG42 S39 Sph. All All 5.665 126.917 126.917S40 Sph. All Z1 38.886 −118.086 −118.086 All Z2 21.921 All Z3 8.637 AllZ4 2.935 All Z5 7.102 22 G5 S41 Sph. All All 6.264 119.224 119.224 S42Sph. All All 0.500 −142.072 −142.072 23 G5 S43 Sph. All All 7.260 81.25581.255 24 G5 S44 Sph. All All 2.600 −93.115 −93.115 S45 Sph. All All0.500 156.198 156.198 25 G5 S46 Sph. All All 5.501 44.318 44.318 S47Sph. All All 0.500 160.913 160.913 26 G5 S48 Sph. All All 3.694 42.72742.727 S49 Sph. All All 7.499 61.123 61.123 Stop S50 Plano All All11.321 Flat Flat 27 G5 S51 Sph. All All 2.000 112.584 112.584 S52 Sph.All All 3.094 26.037 26.037 28 G5 S53 Sph. All All 2.137 108.389 108.389S54 Sph. All All 3.023 30.081 30.081 29 G5 S55 Sph. All All 3.457168.931 168.931 S56 Sph. All All 16.389 −63.194 −63.194 30 G5 S57 Sph.All All 3.904 34.718 34.718 S58 Sph. All All 37.175 44.308 44.308 ImageS59 Y & X Cy F1 Z1 463.940 1029.861 Surface Y & X Cy F2 Z1 390.380−2461.934 Y & X Cy F3 Z1 337.004 −589.389 Y & X Cy F1 Z2 350.000 728.306Y & X Cy F2 Z2 315.862 −22158.909 Y & X Cy F3 Z2 300.000 −1266.833 Y & XCy F1 Z3 331.907 984.085 Y & X Cy F2 Z3 320.000 Flat Y & X Cy F3 Z3300.000 −2186.394 Y & X Cy F1 Z4 437.714 −6078.194 Y & X Cy F2 Z4388.741 −903.184 Y & X Cy F3 Z4 294.968 −696.366 Y & X Cy F1 Z5 816.007−2031.177 Y & X Cy F2 Z5 Flat Flat Y & X Cy F3 Z5 550.000 −1039.893Aperture⁶ Half Sub- Surface Focus Material Diameter Item Group Group No.Shape¹ Position Type Code Name⁴ Supplier⁵ (mm) Object S1 Plano F1 AirPlane F2 F3 1 G1 S2 Sph. All Glass 755523 SYGH51 OHARA 57.00 S3 Sph. AllAir 50.11 2 G1 S4 Sph. All Glass 805254 SF6 SCHOTT 49.83 S5 Sph. F1 Air47.52 F2 F3 3 G1 SG11 S6 Sph. All Glass 805254 SF6 SCHOTT 42.75 4 G1SG11 S7 Sph. All Glass 497816 SFPL51 OHARA 41.81 S8 Sph. All Air 39.59 5G1 SG11 S9 Sph. All Glass 618634 SPHM52 OHARA 39.18 S10 Plano F1 Air38.28 F2 F3 6 G2 S11 X Cyl. All Glass 497816 SFPL51 OHARA 32.83 S12 XCyl. All Air 32.43 7 G2 S13 X Cyl. All Glass 497816 SFPL51 OHARA 32.42S14 Plano All Air 32.65 8 G2 S15 Y Cyl. All Glass 805254 SF6 SCHOTT32.70 S16 Y Cyl. All Air 32.95 9 G2 S17 X Cyl. All Glass 773.5 SLAH66OHARA 33.41 S18 X Cyl. All Air 33.90 10 G2 S19 Y Cyl. All Glass 694.51SLAL58 OHARA 35.18 S20 Y Cyl. All Air 35.45 11 G2 S21 Y Cyl. All Glass487702 SFSL5 OHARA 34.72 S22 Y Cyl. All Air 30.15 12 G2 S23 Y Cyl. AllGlass 497816 SFPL51 OHARA 30.98 S24 Y Cyl. All Air 31.12 13 G3 S25 Sph.All Glass 439950 SFPL53 OHARA 31.53 S26 Sph. All Air 31.55 14 G3 S27Sph. All Glass 720347 SNBH8 OHARA 31.26 15 G3 S28 Sph. All Glass 497816SFPL51 OHARA 30.45 S29 Sph. All Air 30.34 16 G3 S30 Sph. All Glass439950 SFPL53 OHARA 29.87 S31 Sph. All Air 29.38 All All All All 17 G4SG41 S32 Sph. All Glass 717479 SLAM3 OHARA 15.48 S33 Sph. All Air 15.0118 G4 SG41 S34 Sph. All Glass 589612 SBAL35 OHARA 15.14 19 G4 SG41 S35Sph. All Glass 805254 SF6 SCHOTT 15.90 S36 Sph. All Air 16.09 All AllAll All 20 G4 SG42 S37 Sph. All Glass 801350 SLAM66 OHARA 18.84 S38 Sph.All Air 18.83 21 G4 SG42 S39 Sph. All Glass 497816 SFPL51 OHARA 18.95S40 Sph. All Air 19.06 All All All All 22 G5 S41 Sph. All Glass 439950SFPL53 OHARA 18.30 S42 Sph. All Air 18.24 23 G5 S43 Sph. All Glass497816 SFPL51 OHARA 17.95 24 G5 S44 Sph. All Glass 750353 SNI3H51 OHARA17.49 S45 Sph. All Air 17.08 25 G5 S46 Sph. All Glass 497816 SFPL51OHARA 16.91 S47 Sph. All Air 16.40 26 G5 S48 Sph. All Glass 548458 STIL1OHARA 15.84 S49 Sph. All Air 15.14 Stop S50 Plano All Air 13.55 27 G5S51 Sph. All Glass 487702 SFSL5 OHARA 10.20 S52 Sph. All Air 9.93 28 G5S53 Sph. All Glass 516641 SBSL7 OHARA 10.07 S54 Sph. All Air 10.16 29 G5S55 Sph. All Glass 487702 SFSL5 OHARA 10.54 S56 Sph. All Air 10.84 30 G5S57 Sph. All Glass 805254 SF6 SCHOTT 13.24 S58 Sph. All Air 12.90 ImageS59 Y & X Cy F1 Air Surface Y & X Cy F2 Y & X Cy F3 Y & X Cy F1 Y & X CyF2 Y & X Cy F3 Y & X Cy F1 Y & X Cy F2 Y & X Cy F3 Y & X Cy F1 Y & X CyF2 Y & X Cy F3 Y & X Cy F1 Y & X Cy F2 Y & X Cy F3 Notes:- ¹In theSurface Shape column the image surface is not flat to simulateequivalent curved object surfaces through focus distance positions. F1,F2 and F3 and zoom positions Z1, Z2, Z3, Z4 and Z5. ²Paraxial focallengths in the Y-direction at F1 focus position for zoom positions Z1,Z2, Z3, Z4 and Z5 respectively are 40.01 mm, 51.00 mm, 67.98 mm, 95.45mm and 125.01 mm. ³Paraxial focal lengths in the X-direction at F1 focusposition for zoom positions Z1, Z2, Z3, Z4 and Z5 respectively are 20.57mm, 26.21 mm, 34.94 mm, 49.06 mm and 64.27 mm. ⁴In the Material Namecolumn the trade name of the lens material used is given. ⁵In theMaterial Supplier column a manufacturer name is given although there maybe alternative manufacturers. ⁶The data given in the Aperture HalfDiameter column is for circular apertures.

TABLE 2 Focal Length, Anamorphic Squeeze, Illumination and BreathingParaxial Focal Anamorphic Relative Focus Y X Squeeze Illumination² ZoomPosition Position Direction Direction Ratio¹ (%) Breathing³ Z1 F1 40.0120.57 1.946 30.1 0.0 F2 40.16 20.29 1.980 30.9 +0.4 F3 40.33 20.04 2.01330.8 +0.8 Z3 F1 67.98 34.94 1.946 30.1 0.0 F2 68.65 34.52 1.989 30.1+1.0 F3 69.35 34.15 2.031 30.1 +2.0 Z5 F1 125.01 64.27 1.945 30.6 0.0 F2123.15 63.09 1.952 30.6 −1.5 F3 121.48 62.03 1.958 30.6 −2.8 ¹Based onparaxial focal length in Y direction divided by paraxial focal length inX direction. ²At maximum radial image distance from the optical axiswhich is at the corner of the image. ³Based on the percentage differencebetween the paraxial effective focal length in the Y-direction at focusposition F1 and focus positions F2 and F3.

TABLE 3 MTF Performance Data FIELD POSITION Image Normalized HeightImage Height X-direction Y-direction X-direction Y-direction FOCUSPOSITIONS (F) AND ZOOM POSITIONS (Z) PERFORMANCE DATA (mm) (mm) (mm)(mm) F1, Z1 F3, Z1 F2, Z3 F1, Z5 F2, Z5 F3, Z5 Description 0 0 0 0 91.0(R) 90.9 (R) 89.7 (R) 74.7 (R) 75.4 (R) 78.2 (R) Polychromaticdiffraction (Axial) (Axial) 92.2 (T) 92.1 (T) 92.6 (T) 64.2 (T) 72.1 (T)73.1 (T) MTF data (%) 0 8.91 0 1 87.1 (R) 89.8 (R) 89.5 (R) 82.2 (R)59.8 (R) 79.8 (R) at 20 cycles/mm at image (Top of Field) (Top of Field)72.5 (T) 69.3 (T) 75.7 (T) 78.8 (T) 74.4 (T) 69.2 (T) surfaces and atthe following 10.65 0 1 0 63.5 (R) 67.1 (R) 64.5 (R) 57.6 (R) 54.2 (R)65.8 (R) wavelengths 656.3, 587.6, (Side of Field) (Side of Field) 85.9(T) 88.3 (T) 82.6 (T) 53.4 (T) 65.7 (T) 80.7 (T) 546.1, 486.1 and 455.07.47 6.24 0.7 0.7 74.2 (R) 74.7 (R) 81.1 (R) 80.0 (R) 82.3 (R) 79.6 (R)nanometers with respective (70% Corner to Field) (70% Corner of Field)78.6 (T) 78.6 (T) 83.9 (T) 64.7 (T) 75.3 (T) 77.4 (T) weightings 7, 8,9, 7 and 4, 10.65 8.91 1 1 67.1 (R) 66.1 (R) 57.6 (R) 53.1 (R) 63.5 (R)71.7 (R) where (R) = radial and (T) = (Corner of Field) (Corner ofField) 75.3 (T) 74.8 (T) 78.1 (T) 54.0 (T) 62.1 (T) 62.9 (T) tangentialazimuths

TABLE 4 MTF Performance Data FIELD POSITION Image Normalized HeightImage Height X-direction Y-direction X-direction Y-direction FOCUSPOSITIONS (F) AND ZOOM POSITIONS (Z) PERFORMANCE DATA (mm) (mm) (mm)(mm) F1, Z1 F3, Z1 F2, Z3 F1, Z5 F2, Z5 F3, Z5 Description 0 0 0 0 90.3(R) 90.3 (R) 89.3 (R) 73.2 (R) 74.0 (R) 76.9 (R) Polychromaticdiffraction (Axial) (Axial) 91.5 (T) 91.8 (T) 93.2 (T) 64.6 (T) 74.9 (T)74.1 (T) MTF data (%) 0 8.91 0 1 87.9 (R) 89.6 (R) 89.8 (R) 82.7 (R)61.2 (R) 82.1 (R) at 20 cycles/mm at image (Top of Field) (Top of Field)70.5 (T) 67.0 (T) 73.5 (T) 79.8 (T) 71.6 (T) 65.6 (T) surfaces and atthe following 10.65 0 1 0 62.1 (R) 65.6 (R) 64.5 (R) 57.1 (R) 52.2 (R)63.3 (R) wavelengths 656.3, 587.6, (Side of Field) (Side of Field) 86.9(T) 88.5 (T) 85.1 (T) 54.1 (T) 70.4 (T) 82.2 (T) 546.1, 486.1 and 455.07.47 6.24 0.7 0.7 73.3 (R) 73.7 (R) 80.5 (R) 79.6 (R) 81.4 (R) 78.1 (R)nanometers with respective (70% Corner to Field) (70% Corner of Field)77.6 (T) 77.3 (T) 84.9 (T) 66.1 (T) 77.1 (T) 77.4 (T) weightings 7, 8,9, 7 and 4, 10.65 8.91 1 1 67.9 (R) 66.7 (R) 58.3 (R) 54.0 (R) 64.4 (R)71.5 (R) where (R) = radial and (T) = (Corner of Field) (Corner ofField) 74.3 (T) 73.7 (T) 77.4 (T) 53.4 (T) 612 (T) 61.3 (T) tangentialazimuths

TABLE 5 MTF Performance Data FIELD POSITION Image Normalized HeightImage Height X-direction Y-direction X-direction Y-direction FOCUSPOSITIONS (F) AND ZOOM POSITIONS (Z) PERFORMANCE DATA (mm) (mm) (mm)(mm) F1, Z1 F3, Z1 F2, Z3 F1, Z5 F2, Z5 F3, Z5 Description 0 0 0 0 91.3(R) 90.9 (R) 90.4 (R) 77.2 (R) 77.9 (R) 80.3 (R) Polychromaticdiffraction (Axial) (Axial) 92.9 (T) 92.0 (T) 92.2 (T) 62.5 (T) 68.3 (T)70.4 (T) MTF data (%) 0 8.91 0 1 85.5 (R) 89.6 (R) 88.8 (R) 79.7 (R)55.7 (R) 87.6 (R) at 20 cycles/mm at image (Top of Field) (Top of Field)73.6 (T) 70.8 (T) 76.4 (T) 77.2 (T) 77.6 (T) 71.1 (T) surfaces and atthe following 10.65 0 1 0 64.7 (R) 68.3 (R) 64.0 (R) 58.1 (R) 56.8 (R)68.5 (R) wavelengths 656.3, 587.6, (Side of Field) (Side of Field) 84.1(T) 87.7 (T) 80.3 (T) 51.6 (T) 70.9 (T) 77.6 (T) 546.1, 486.1 and 455.07.47 6.24 0.7 0.7 75.3 (R) 75.7 (R) 81.4 (R) 80.0 (R) 83.0 (R) 81.2 (R)nanometers with respective (70% Corner to Field) (70% Corner of Field)79.4 (T) 79.5 (T) 83.1 (T) 61.9 (T) 72.7 (T) 76.0 (T) weightings 7, 8,9, 7 and 4, 10.65 8.91 1 1 65.2 (R) 64.0 (R) 55.9 (R) 50.3 (R) 61.3 (R)71.4 (R) where (R) = radial and (T) = (Corner of Field) (Corner ofField) 75.1 (T) 75.1 (T) 78.3 (T) 52.7 (T) 61.4 (T) 62.2 (T) tangentialazimuths

I claim:
 1. An anamorphic objective zoom lens comprising along anoptical axis and in order from an object space to an image space: anegative (−) power spherical first lens group; an anamorphic second lensgroup; a spherical third lens group, a zoom fourth lens group, apositive (+) power spherical fifth lens group and an aperture stop;wherein said aperture stop is located in a position selected from one ofthe following locations: within said spherical fifth lens group, betweensaid zoom fourth lens group and said positive (+) power spherical fifthlens group and between said positive (+) power spherical fifth lensgroup and the image space, wherein at least one lens element of saidspherical third lens group and at least one lens element of saidspherical fifth lens group are independently axially adjustable tocompensate for thermal defocus in image space for at least two focallengths within the focal length range.
 2. The anamorphic objective zoomlens group of claim 1 wherein said spherical third lens group is apositive (+) power spherical third lens group.
 3. The anamorphicobjective zoom lens of claim 1 wherein said aperture stop is locatedwithin said positive (+) power spherical fifth lens group.
 4. Theanamorphic objective zoom lens of claim 1 having a focal length withinthe range of from at least 35 mm to 140 mm.
 5. The anamorphic objectivezoom lens of claim 1 having a focal length within the range of 40 mm to125 mm.
 6. The anamorphic objective zoom lens group of claim 1 whereinsaid spherical third lens group is a negative (−) power spherical thirdlens group.
 7. The allomorphic objective zoom lens of claim 1 whereinsaid anamorphic second lens group has at least one cylindrical surfacein a first direction and at least one cylindrical surface in a directionsubstantially perpendicular to said first direction.
 8. The anamorphicobjective zoom lens of claim 1 wherein said anamorphic second lens grouphas focal lengths in perpendicular directions which differ by a ratio ofabout two times.
 9. The anamorphic objective zoom lens of claim 1wherein said lens groups are fabricated of lens elements made of glass.10. The anamorphic objective zoom lens of claim 1 wherein said sphericallens groups each comprise a lens element with a rotationally symmetricalsurface shape about said optical axis.
 11. The anamorphic objective zoomlens of claim 1 wherein said anamorphic second lens group comprises alens element with a non-rotationally symmetrical surface about saidoptical axis.
 12. The anamorphic objective zoom lens of claim 1 whereinsaid anamorphic second lens group comprises seven cylindrically surfacedlens elements with eight Y cylinders, five X cylinders and one planosurface shapes.
 13. The anamorphic objective zoom lens of claim 1wherein said spherical first lens group comprises five lens elements,three of which are axially moveable relative to the other.
 14. Theallomorphic objective zoom lens of claim 1 wherein said spherical thirdlens group comprises four lens elements.
 15. The anamorphic objectivezoom lens of claim 1 wherein said spherical fifth lens group comprisesnine lens elements.
 16. The anamorphic objective zoom lens of claim 1wherein said zoom fourth lens group comprises five lens elements. 17.The anamorphic objective zoom lens of claim 1 wherein said zoom fourthlens group comprises two lens sub groups, said sub lens groups havingthree lens elements and two lens elements, respectively, of which bothlens sub groups are axially moveable.
 18. The anamorphic objective zoomlens of claim 1 wherein said spherical third lens group comprises lenselements and said spherical fifth lens group comprises lens elements,wherein said lens elements of said spherical third lens group aremoveable together, said lens elements of said spherical fifth lens groupare moveable together, and said spherical third lens group and saidspherical fifth lens group are independently axially adjustable tocompensate for thermal defocus in image space for at least two focallengths within the focal length range.
 19. The anamorphic objective zoomlens of claim 1 wherein thermal defocus in image space is compensated insaid focal length range.
 20. The anamorphic objective zoom lens of claim1 wherein said anamorphic objective zoom lens has a substantiallyconstant overall length.
 21. The anamorphic objective zoom lens of claim1 having a focal length within the range of from at least 35 mm to 140mm in.
 22. The anamorphic objective zoom lens of claim 1 wherein saidthird lens group comprises an element and said spherical fifth lensgroup comprises an element, wherein said element of said spherical thirdlens group and said element of said spherical fifth lens group aremoveable.
 23. An anamorphic objective zoom lens comprising along anoptical axis extending from an object space to an image space: aspherical lens group adjacent the object space; a spherical lens groupadjacent the image space; an anamorphic lens group located between saidspherical lens group adjacent the object space and said spherical lensgroup adjacent the image space; a zoom lens group; a further sphericallens group situated between the anamorphic lens group and the zoom lensgroup, and an aperture stop situated within one of the followinglocations: within said spherical lens group adjacent the image space,between said spherical lens group adjacent the image space and said zoomlens group and between said spherical lens group adjacent the imagespace and the image space wherein at least one lens element of saidfurther spherical lens group and at least one lens element of saidspherical lens group adjacent the image space are independently axiallyadjustable to compensate for thermal defocus in image space for at leasttwo focal lengths within the focal length range.
 24. The anamorphicobjective zoom lens of claim 23 wherein said spherical lens groupadjacent the object space has a negative (−) power and said furtherspherical lens group has a positive (+) power.
 25. The anamorphicobjective zoom lens of claim 23 wherein said further spherical lensgroup has a positive (+) power and said spherical lens group adjacentthe image space has a positive (+) power.
 26. The anamorphic objectivezoom lens of claim 23 wherein said anamorphic lens group comprises atleast one cylindrical surface in a first direction and at least onecylindrical surface in a direction substantially perpendicular to saidfirst direction.
 27. The anamorphic objective zoom lens of claim 23wherein said anamorphic lens group comprises at least one cylindricalsurface in an X direction and at least one cylindrical surface in a Ydirection.
 28. The anamorphic objective zoom lens of claim 23 whereinthe anamorphic objective zoom lens has a substantially constant overalllength.
 29. The anamorphic objective zoom lens of claim 23 having afocal length within the range of from at least 35 mm to 140 mm.
 30. Theanamorphic objective zoom lens of claim 23 wherein said lens element ofsaid further spherical lens group and said lens element of saidspherical lens group adjacent said image space are moveable.
 31. Theanamorphic objective zoom lens of claim 23 wherein said furtherspherical lens group comprises a lens element and said spherical lensgroup comprises a lens element, wherein said lens element of saidfurther spherical lens group and said lens element of said sphericallens group adjacent said image space are moveable.
 32. The anamorphicobjective zoom lens of claim 23 wherein said further spherical lenswrong comprises a lens element and said spherical lens group comprises alens element, wherein said lens elements of said further spherical lensgroup are moveable together, and said lens elements of said sphericalfifth lens group are moveable together, and said further spherical lensgroup and said spherical fifth legs group are independently axiallyadjustable to compensate for thermal defocus in image space for at leasttwo focal lengths within the focal length range.
 33. The anamorphicobjective zoom lens of claim 32 wherein thermal defocus in image spaceis compensated within said focal length range.
 34. The anamorphicobjective zoom lens of claim 32 wherein the anamorphic objective lenshas a substantially constant overall length.
 35. The anamorphicobjective zoom lens of claim 32 having a focal length within the rangeof from at least 35 mm to 140 mm.